WR450 starter motor mod to bigger brushes

dknibbs

Hi guys. I recently bought a WR450 2005 model. The bike was cheap enough however needed some work done. One of the issues was that the old startermotor was missing. Quick check and I found one on ebay for half the price to a new one from my local dealer. I fitted the new starter and after two outrides I noticed a problem with the starter’s ability to turn the motor over, seem to get stuck and after awhile would barely turn over. I did some online research and it seems to be quite a common problem to find a dead spot on the starter motor where you have to then put the bike in gear and move the bike forward and backwards just moving the starter over slightly. Others recommended I check the cover is on straight and that I should give it a slight tap with a rubber mallet above where the thrustgear sits, this seemed to work but for a very brief moment only.

After numours taps with the mallet and taking of and replacing the starter, I took it back to the basics and tried to run the starter on its own. It was then that I realised the problem was infact with the starter motor. I took the starter off and stripping it I found to my horror that one of the commutator (comm) points on the armature has come loose and was busy wrecking the brushes. I took it to my local auto electrician and according to him it is a common sypmthom from over cranking the starter and causing it to overheat.

Comm that came loose and brushes that got wrecked.

So step number next was to try and fix this setup as I could not afford to buy another under powered (in my opinion) starter motor. I used a small drillbit to open up and allow for more epoxy under the comm, lapped on quite abit of epoxy and left it for a few days. Once completely hardened I put the armature in my drill and used a metal file to smooth out the comm points as the repaired comm was slightly lower than the rest of them and would catch on the new brushes.

After comm was reattached and cleanedup abit.

Next I removed the plastic base holding the brushes, I foud that the plastic sleevs that the brushes sit in had cracked and fallen apart. Now I had nowhere to keep my brushes (still going to make some). I decided that I would use the leftover holes and using more epoxy made new slots for the brushes to sit in. This inturn allowed for bigger brushes (almost double the size) wich I hoped will help with the head distribution and allow the starter to run a little longer before everything starts overheating.

Old brush sleeve that broke

New sleeve from epoxy

Now to get new brushes, this in it self was quite a challenge as the small brushes all had very thin connecting wires and I could see these brushes would need quite a thick wire. I finaly managed to get some brushes from a parts store that I could cut to size. Using a dremmel tool I managed to get them to fit nice and snug into the now new slots. I soldered my now new and improved brushes back into place, reassembled the whole setup and tested the starter on its own (no load yet) and it turned nicely however maybe a little slower than before.

I did find that the starter still had a dead spot where I had to turn it over by hand before it would spin again so it seems that issue will always be there.

Next step is to see how it is going to perform on the bike having to turn the motor over.

New brush compared to the original brush

The brush I used to make the new brush, not sure for what vechile this is.

Some duct tape to insulate the brush and spring on the positve lead from the case